Disk drives can comprise a disk surface and a head connected to a distal end of an actuator arm which is rotated about a pivot by a voice coil motor (VCM) to position the head radially over the disk surface. The disk surface typically comprises a number of concentric data tracks each partitioned into a number of data blocks. Access operations are performed by seeking the head to a target data track, and performing a write/read operation on the data blocks within the data track. The disk surface typically comprises embedded servo sectors having position information recorded therein, such as coarse position information (e.g., a track address) and fine position information (e.g., servo bursts). A servo controller processes the servo sectors to position the head over the target data track.
An air bearing forms between the head and the disk surface due to high speed rotation of the disk surface. Since the quality of the write/read signal depends on the fly height of the head, conventional heads (e.g., magnetoresistive heads) may comprise an actuator for controlling the fly height. Any suitable fly height actuator may be employed, such as a heater which controls fly height through thermal expansion, or a piezoelectric (PZT) actuator. However, if the fly height of the head is too low, undesirable wear and damage to the head can occur as a result of contact between the head and the disk surface. On the other hand, a head fly height that is too high can result in undesirable degradation in write/read performance of the disk drive.